Abstract

The noise of an efficient EDFA is characterized, and it is shown that at optimum gain efficiency the EDFA exhibits an increased NF. In addition, with the conventional (co-directionally pumped) configuration it is virtually impossible to obtain a combination of high gain (>30 dB) and quantum-limited NF. Incorporating an isolator in the EDFA overcomes these problems, and we have demonstrated an amplifier with 51 dB gain and 3.1 dB NF for only 45 mW of pump power. Constant power optical amplifiers are discussed, and we show that simply inducing a differential loss between pump and signal in the EDFA achieves an optical power limiting action with a >30 dB dynamic range. Experimental results are given. We report the generation of a high-purity 70-Gbit/s cw soliton train. The technique is based on the nonlinear propagation and compression of a dual-frequency beat signal, amplified with an erbium-doped power amplifier and propagated through a dispersion decreasing fiber.

© 1992 Optical Society of America